Ever wonder why your floors feel cold in January even after you've insulated the attic? The culprit is often the rim joist โ that narrow band of framing that sits right on top of your foundation wall. In Northeast Arkansas, where January lows routinely hit the mid-20s, an uninsulated rim joist is basically a screen door on your basement.
So what does rim joist insulation actually cost? For a typical Jonesboro-area ranch home, expect to pay roughly $1.50โ$2.50 per board foot for 2-lb closed-cell spray foam applied directly to the rim joist cavity. A 1,500 SF footprint usually has 100โ150 linear feet of rim joist, which translates to a job in the $400โ$900 range depending on cavity depth and access.
Why closed-cell specifically? Because rim joists are exposed to outside air AND moisture from the crawl space or basement below. Closed-cell foam hits R-6 to R-7 per inch, so even a 2-inch application clears R-12 โ meeting IRC R402.2.1 requirements for Climate Zone 3 (where Jonesboro and Trumann both sit). Open-cell foam is too vapor-permeable here; you'd be inviting wood rot within a few years.
A pro can typically spray an entire rim joist in 2โ4 hours. It's one of those jobs with an outrageously fast payback โ most homeowners see the difference on their first Entergy bill after the work is done. Pair it with air sealing around any penetrations (pipes, wires) and you've closed one of the most common thermal bypasses in Arkansas housing stock.
If you're not sure whether your rim joist is insulated, peek into your crawl space or basement and look at that top band of wood. If you see bare lumber, you're losing money every day.
Reply or DM us for a free rim joist estimate โ we serve Jonesboro, Trumann, Paragould, and the surrounding area.